lcd display viewing angle quotation

Updated: Oct 28, 2019:Despite all the advances in LCD display technology viewing angle is still an important topic, panel viewing angles are still poor, good, better and best, but none are 100% perfect.

The viewing angle of an LCD panel is typical given based on the normal aspect ratio which is generally landscape for the types of LCD panels we work with. It is quoted for both horizontal and vertical in degrees from perpendicular to the display or as a total of left & right and up & down. So for example the newer IPS panels now claim up to 89 degree viewing angle from perpendicular for both horizontal and vertical.

Specifications are no replacement for actually seeing and evaluating an LCD panel, the reason is that there can be characteristics that the specifications don’t mention. For example I have seen an LCD panel with excellent viewing angle specifications but when testing it I could see a color shift at around 45 degrees from perpendicular.

Further to the previous point, even though LCD panel specification may quote H (horizontal) & V (vertical) viewing angles the performance in portrait model may be quite different to landscape mode.

I realize not every application needs or even suits having a wide viewing angle. Digital signage displays clearly benefit from a wide viewing angle if used in a poster or menu board but some overhead information displays need a good 6 o’clock viewing angle, ie when viewed from below, but the 12 o’clock viewing angle may not be critical.

IPS panels have had quite a few years of being a leading technology for excellent viewing angle with not only impressive specifications but genuinely excellent results. More recently companies like AUO have been showing panels with a new technology that appears to provide not only equivalent viewing angles but also excellent color fidelity over the range of viewing angles.

At this time the viewing angle of a LCD panel is not a tunable setting, it is a fixed part of the LCD panel design. Filters can be added by reworking the panel or adding to the front but these will typically limit rather than extend the viewing angle.

A TN or Twisted Nematic TFT LCD is a cost-effective high performance LCD. It offers good brightness performance and fast response times. However, it suffers in one key area and that is its viewing cone. TN LCD’s typically have three good viewing angle directions. In these directions the image is typically clear and colors are consistent up to 80 degrees from the center of the LCD. The remaining viewing direction is usually good through 40-50 degrees from center. Afterwards, the image is likely to invert, almost appearing like an x-ray.

Viewing angle is a very important factor when evaluating LCD display"s performance. Understanding how to locate the optimum viewing angle and choose the right LCD display will make your product looks sharp without extra cost.

LCD viewing angle is the maximum angle from which customer can view the screen well. "Viewing well" is commonly recognized as having at least 10:1 contrast and without grayscale inversion.

At time of manufacturing, LCD manufacturer designs LCD panel in a way that it is best viewed from an angle (called Bias) offset from the perpendicular by certain degrees, to accommodate as many applications as possible. Viewing angle is the angle covers both side of Bias angle, where the LCD is still "viewing well".

When reading an LCD"s specification, you will see the term "viewing direction". Viewing direction is defined following the format of a clock. Like figure below, Z axis is Normal, X axis is Horizontal and Y axis is Vertical. An LCD"s viewing angle "above" Z axis is having 12 o"clock viewing direction. So 6 o"clock viewing direction LCD is best viewed from "below" Z axis.

Theoretically, LCD manufacturer can produce LCD with 3, 12, 9 and 6 o"clock viewing direction. But in practice, we usually look at LCD display from 12 or 6 o"clock angle.

Using a simple TN type TFT LCD as example, its viewing angle is typically 45~65 degrees. Adding extra wide polarizer film (EWP) to the TN type LCD, the viewing angle may be increased about 10 degrees. Similarly, an O-film enhancement polarizer will widen the viewing angle to 75 degree in each direction. However, these enhancements bring along contrast reduction. Adjusting LCD contrast is necessary.

Using a liquid crystal display with proper viewing angle is very important to your product"s success. And we should keep in mind that optimized contrast is crucial, too. Both parameters define the visual appearance of the LCD display and the appeal of your product. Choices are based on cost performance trade offs.

For example, if your project requires a wide viewing angle 2.4" TFT LCD. TN TFT panel with O-film solution might be better than using IPS LCD. Topway engineers are here to help you making those design decisions.

The viewing angle is the angle at which the image quality of an LCD degrades and becomes unacceptable for the intended application. Viewing angles are usually quoted in horizontal and vertical degrees with importance dependent on the specific application. As the observer physically moves to the sides of the LCD, the images will degrade in three ways. First, the luminance drops. Second, the contrast ratio usually drops off at large angles. Third, the colors may shift. Most modern LCD’s have acceptable viewing angles even for viewing from the sides.

For LCD’s used in outdoor applications, defining the viewing angle based on CR alone is not adequate. Under very bright ambient light conditions the display is hardly visible when the screen luminance drops below 200 nits. Therefore, the viewing angles are defined based on both the CR and the Luminance.

When your customer compares your product with your competitors, the correct choice of the LCD viewing direction makes the difference between a product that looks ‘okay’ and a product that grabs and holds your customer’s attention. If the display on our product looks sharp, your product looks sharp and this can be accomplished at no extra cost by understanding how to locate the optimum viewing angle.

LCD display modules are built to provide the sharpest contrast and readability in one of four directions called the ‘the viewing angle’ or ‘optimum viewing direction.’ The four directions follow the format of a clock. With twelve o"clock viewing (12:00) being the top view and six o"clock (6:00) the bottom.

When specifying the best viewing direction for your new design, put yourself in the place of your customer. “From what direction will this display be viewed?” In other words, where will your end user be standing when they use your product?

Whereas a very tall person, say 6’5” or taller, (think David and Goliath) pumping gas into their car, would look down at the LCD display, watching their dollars fly by as they fill up the tank. This would be a twelve o’clock (12:00) or top view.

Two other possible viewing angles include: Three o’clock (3:00 or left side view) and nine o’clock (9:00 or right-side view) but rarely used, 6:00 view is the default value for 80% of all monochrome displays. So, if you’re not sure which viewing angle to choose, go with 6:00.

There is no cost difference between viewing angles, but for TFT"s there may be a longer lead-time or MOQ (Minimum Order Quantity) than for monochrome displays.

Fellowes D, Draper R, Sabatier C, Fields M, Prache O (2002) Performance test results for SVGA+ color AMOLED microdisplays. Microdisplay 2002. SID, Cambell, pp 37–40

Huang YY, Chen YM, Lin CC, Lee CR, Yu HT (2007) Autonomous compensation in improving viewing angle dependent color deviation and maintaining contrast ratio of vertically-aligned TFT-LCD. IDW "07, Sapporo, pp 1877–1580

Suzuki S, Takizawa H (2002) Characterization of color shift and grayscale for wide-viewing-angle AM-LCD technologies. Euro display "02. Nice, pp 107–110

Different Glass structure comes with different viewing angles. Please refer to the image chart (right) to see unedited pictures of the actual glass types.

This monitor will display a 250:1 contrast ratio when viewed head on or at a 90° angle from the surface of the monitor. The contrast ratio will decline as you view the display from the side eventually going down to 10:1 or 5:1 contrast ratio at an angle of 70° from head on. As you move away from the maximum contrast at the straight on viewing position, the brightness of the white may increase or decrease and the black may increase or decrease. However, the contrast (ratio of the two) will decrease as you move away from normal viewing. Please note, this is just a general representation and not factual for every monitor with 140° viewing angle. All values are estimates.

Other factors such as the display"s brightness, ambient light and contrast conditions all play a part in the readability of the display. As mentioned above, viewing angle is defined using only the contrast ratio. However, even within this standard viewing angle, the colors or tones on the display panel may look different from the real color/tone, or they may become invisible, depending on the combination of displayed colors (background color, text color and switch color). For example, if the background color is bright and you look at the screen from below, the colors may appear inverted so that the text color and switch color darken to the point where they become invisible. Or, when the background color is dark and you look at the screen from above, the colors may again appear inverted, so that the text color and switch color brighten to the point that they become invisible. As a result, be sure to choose your screen colors carefully, so they produce an effective combination for the LCD panel"s operation environment.

When the voltage is applied to the electrode of the LCD, the light (brightness) passing through the LCD will change. The reaction time from its change to the stable time is called the light’s reaction time（response time), which divided into Tr and TF.

Tr refers to the reaction time of LCD when the voltage rises to a stable state (the time required for the light penetration rate to change from 10% to 90% after pressure). Tf refers to the reaction time of LCD when the voltage drops to a stable state(the time required for the light penetration rate to change from 90% to 10% after pressure).

If the luminance is too low, the screen will be darker; and the display will be clearer when high luminance. However, if the screen luminance is too high, the eyes will be tired of too long.

NTSC refers to the degree of bright colors. If the RGB primary colors are more bright, the display can display a wider range of colors. The color range can be displayed with the primitive color range divided by the color range specified by NTSC.